<!-- 
    
 -->
<html>

<head>
    <title>Canvas tutorial</title>
    <script type="text/javascript">
        function draw() {
            var ctx = document.getElementById('canvas').getContext('2d');
            for (var i = 0; i < 6; i++) {
                for (var j = 0; j < 6; j++) {
                    ctx.fillStyle = 'rgb(' + Math.floor(255 - 42.5 * i) + ',' +
                        Math.floor(255 - 42.5 * j) + ',0)';
                    ctx.fillRect(j * 25, i * 25, 25, 25);
                }
            }
        }
    </script>
    <style type="text/css">
        canvas {
            border: 1px solid black;
        }
    </style>
</head>

<body onload="draw();">
    <canvas id="canvas" width="500" height="500"></canvas>
</body>

</html>